1. Field of the Invention
The present invention relates to a disposable container, methods of making the disposable container and machines and devices that can be used in the method and/or to make the disposable container. More particularly, the present invention relates to a container made of expandable thermoplastic resin beads with a label sheet disposed about the outer surfaces of the sidewall of the container. The container can be used for holding hot or cold liquids, such as beverages, or foods such as instant noodles, soups, fried chicken, and the like.
2. Background Art
The manufacture of molded articles, such as containers, for example cups, bowls, and the like from expanded thermoplastic particles is well known. The most commonly used thermoplastic particles are expandable polystyrene particles known as EPS. Typically, polystyrene beads are impregnated with a blowing agent, which boils below the softening point of the polystyrene and causes the impregnated beads to expand when they are heated.
The formation of molded articles from impregnated polystyrene beads is generally done in two steps. First, the impregnated polystyrene beads are pre-expanded to a density of from about 0.5 to 12 pounds per cubic foot or 5 to 150 grams per liter. Second, the pre-expanded beads are heated in a closed mold to further expand the pre-expanded beads to form a fused article having the shape of the mold.
The expandable polystyrene particles used to make foam containers are generally prepared by an aqueous suspension polymerization process, which results in beads that can be screened to relatively precise bead sizes. Typically, bead diameters are within the range of from about 0.008 to about 0.02 inch (about 0.2 to about 0.5 mm). Occasionally, cups are made from particles having bead diameters as high as 0.03 inches.
It is desirable to provide containers with thin walls that provide adequate insulating and structural properties and that contain high quality printed graphics on the outside surfaces of the container.
One method of obtaining printed graphics on the outside surfaces of a container is by molding the container and then printing on the outside surface of the container. However, this approach typically results in lower print quality and does not convey the desired commercial image.
Another method that has been employed is to pre-print labels that are applied to the outside surfaces of a container after molding. As an example, U.S. Patent Application Publication No. 2006/005917 A1 discloses a method and apparatus for producing labeled, plastic foam containers, such as labeled EPS cups that includes using a heated secondary mold to thermally bond a label to a plastic cup. Although high quality graphics can be applied to containers using these methods, labeling consistency, due to the many mechanical steps involved is a problem. Also, the seam formed where the ends of the label meet often leaves a gap between the ends of the label sheet, where the container surface can be seen, the label can be poorly aligned vertically overlapping the container rim or base, and/or the label ends overlap forming a raised seam that can be aesthetically unattractive, can lead to inefficient cup stacking, as well as providing a site where labels can be peeled from the container surface.
Attempts to solve the above described problems have been attempted through in-mold labeling techniques. As an example, WO 01/85420 discloses a method and apparatus for molding an expanded plastic container having a label material affixed to an external wall of the container during the molding cycle. In this method, a label to be affixed to a molded container is transferred by a plunger having a vacuum pick-up head from a stack of flat labels to a dummy male core and is wrapped about the dummy core. The latter is mounted on a carriage, which is reciprocal between the label pick-up station and a vertically oriented molding station having a molding tool for molding expanded plastic material. When the dummy core enters the female mold part, the label carried by the core is transferred to and retained on the wall of the female mold part. Particular problems with this method include inconsistent label placement and molding consistency as the many mechanical steps and vertical orientation cause shifting of the machine parts and label. These problems result in a large amount of waste, i.e., containers that are molded and/or labeled improperly and cannot be used.
Additionally, in some instances, improper label placement can result in containers that leak.
There is an unmet need in the art for methods and equipment to produce smooth surfaced consistently labeled containers that can be manufactured with low waste at commercial scale and overcome the above-described problems.